With the development of high-speed transmission, as well as precise and miniaturized design of electronic products, the heat density generated in the electronic product keeps increasing. Thus, heat dissipation performance of the product becomes a key performance index. As an important member of components of electronic products, poor heat dissipation of the rigid-flex board products may reduce the electrical performance of the components, or even result in destruction of the product. Thus, a rigid-flex board product with good heat dispersion performance determines its importance role in the application more significantly.
In order to solve the problem of heat dissipation, there are several methods applied in PCB products each having some shortages that it is difficult to satisfy the requirement of high-efficiency cooling for a rigid-flex board product, including:
(1) a board combined of a copper seat or an aluminum seat and a PCB, in which a single-layer or multilayer PCB is grafted with a copper seat or an aluminum seat that only the contact region of the PCB plays a role in heat dissipation,
(2) an aluminum or copper base board, generally a single sided board in which one side is used for circuit, and the other side is used for heat dissipation, so that the number of circuit layers is limited:
(3) a conductive heat dissipation silver or copper paste board, in which heat from the surface electronic elements can be quickly transferred to a corresponding grounded large copper surface for heat dissipation, by a hole clogging technique with aluminum or copper base with a certain heat-conducting property, which has high cost, particularly of the large copper surface;
(4) a PCB with buried copper block, in which a copper block is embedded in a multilayer PCB for local heat dissipation, but the CTE of the copper block does not match that of the dielectric layer of the PCB, so that the reliability is limited; and
(5) a metal-based sandwich PCB, as a development version of the PCB with buried copper block, in which a metal core layer as a separate non-circuit layer is pressed together with a circuit layer of the PCB so that hear can be dissipated around the board; but it is difficult to process the metal core as a separate layer, and it is difficult to guarantee the reliability.